Dear Lifehacker,
My laptop fan is super loud, and I can't seem to get it to quiet down. It's all BRRRRRRRRRR the whole day, and I'm like FUUUUUUUUUUUU and slap it BAAAAAM and it won't quit making noise. Help!

There are a number of reasons your computer's fan could be noisy, but most of them boil down to "it's just too hot in there". Here are a few things you can try to get it running a bit cooler and quieter.

Check Your Processes

Your CPU fan will start blowing like mad if you're running CPU-intensive processes, like games or video conversions. If you aren't doing one of these things, you'll definitely want to see if another process is eating up your CPU for no reason.

Hit Ctrl+Shift+Esc to bring up the Task Manager (or, if you're on a Mac, open up Activity Monitor under /Applications/Utilities). Check the processes tab to see if anything's taking up an abnormally large precent of your CPU's power—usually, if something's out of control, it'll be up close to 100. (Note that the System Idle Process is allowed to be that high—most other programs are suspicious, though). If everything's relatively low (single-digits or maybe the tens), then it isn't your CPU going out of control, it's the fan itself.

There's also a chance it's your video card's fan that's going out of control, in which case you might want to update your drivers. It's usually a long shot, but it's worth a try.

Cool Down Your Computer

There's a good chance that your computer's just too darn hot, for one reason or another. Perhaps your computer tower is stashed inside a small cupboard with little airflow, or you're using your laptop on your lap and not letting enough heat escape. This will cause your computer to overheat, even if it isn't taxing itself, and it'll spin your fans like crazy.

If you're on a desktop, make sure you have adequate airflow in and around your computer tower. If it's in a little cupboard, move it outside the desk for awhile and see if that helps. If you're on a laptop, try using one of the manyDIY laptop stands we've featured (or even a DIY laptop cooler) to cool it down—that may quiet those noisy fans.

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Also, as summer approaches, make sure you aren't keeping your laptop out in the sun for too long. Your laptop has heat limits, and the closer you get to them, the more likely it is to malfunction and go crazy with its fans.

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Clean Your Fans

If none of that is helping, you're going to have to open up your computer and dig around. You'll definitely want to clear all the dust out of your machine, since this can cause overheating which could make your fans blow loudly. And, if your fans are really dusty, they could get especially noisy too. We've talked about how to do some of this before (and even shown you in video form)—all you need is some compressed air and some oil.

If all else fails, you may need to replace the fan entirely. You can usually buy fans at electronics stores like Micro Center, Fry's or even Best Buy (though you might need to get laptop fans through the laptop manufacturer, depending).

It's worth noting that, while there are a lot of tools out there like Speedfan and smcFanControl that you can use to manually slow your fans down, I wouldn't recommend using them. They're generally for advanced users only, and if your fan is running loud, there's probably a reason—usually that it's too hot in there. If you slow it down without cooling off your computer, it could overheat. That said, these tools could be useful for figuring out which fan is making all the noise, but other than that, I wouldn't recommend using them until you've actually fixed the problem.

Hopefully this gives you a bit of direction into fixing your problem. If you guys have any other suggestions, be sure to share them with us in the comments!